Recently, operating-system-level virtualization has become more and more widely used in cloud computing and platform as a service (PaaS) frameworks. Operating-system-level virtualization is a server-virtualization method where the operating system kernel allows multiple isolated user space instances called containers. On the Linux operating system, with support from kernel namespaces and the cgroups mechanism, emerging container solutions such as Docker and LXC have been attracting more and more attention and are currently in rapid development. Compared with a traditional virtual machine, a container uses a smaller image size, launches faster, and costs less resources (e.g., memory, processing clock cycles), thus making the container a lightweight and fast virtualization solution.